I used to work right down the street from the Kopper Kitchen, and it was always one of the first places my co-workers would try for lunch. I say one of the first because they are *always* packed for lunch.
There's nothing fancy here, but who cares when the food is so good? Waitstaff is no-nonsense, but they're busy and trying to get your food to you (and everyone else) as fast as possible. Their reuben sandwich was amazing. Think they serve breakfast as well.